JPH04230955A - High-temperature fuel cell - Google Patents

Abstract

PURPOSE:To reduce the contact resistance between the cathode and current collector of a high-temperature fuel cell and improve the cell output. CONSTITUTION:In a high-temperature fuel cell formed with a cathode 12 on the surface of a high-temperature electrolyte 1 and having a current collector 14 in contact with the cathode 12, the cathode 12 is made of La1-xSrxMo3, where M indicates Mn, Co or Ni, and at least one kind among Pd, Cr, Ti, Zn, Nb and Ta is provided on the surface of the electrolyte 11 faced to the cathode 12, the surface of the cathode 12 faced to the current collector 14 and/or the surface of the current collector 14 faced to the cathode 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-temperature fuel cells, and more particularly to a technique for reducing contact resistance between a cathode and a current collector and improving cell output.

0002

[Prior Art] As for high-temperature fuel cells, a pilot plant of approximately 5KW has already been manufactured and operated at Westinghouse Electric Company in the United States, but this is a type called cylindrical and has a low power density. There is a drawback that it is difficult to downsize. On the other hand, the flat plate type has 1
Although it has the characteristic that it is possible to increase the power density by reducing the thickness per stage, there are few demonstration examples because gas sealing is difficult.

Generally, stabilized or partially stabilized zirconia is used as the electrolyte, and La(Sr)M is used as the cathode.
nO3 or La(Sr)CoO3, and Ni/ZrO2 as the anode. Further, metal or LaCrO3 is used as the current collector.

0004

[Problems to be Solved by the Invention] Platinum and other materials were initially used as cathodes, but perovskite oxides were used instead of platinum because they have high catalytic activity against oxygen dissociation reactions and improve battery performance. is often used. However, when a perovskite oxide such as La(Sr)MnO3 or La(Sr)CoO3 is used as a cathode, the contact resistance between the cathode and the current collector or electrolyte, especially the contact resistance between the cathode and the current collector, increases. , the output is reduced by that amount.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a high-temperature electrolyte having a structure in which a cathode is formed on one surface of a high-temperature electrolyte and a current collector is brought into contact with the cathode. In a fuel cell, the cathode is La1-x S
rxMO3 (wherein M represents Mn, Co or Ni) and faces the cathode of the electrolyte,
Pd, Cr, Mn, Ti,
The present invention provides a high-temperature fuel cell characterized in that at least one of Zn, Nb, and Ta is present.

[0006] The cathode used in the present invention is La1-x S
rxMO3 (wherein M represents Mn, Co, or Ni). The value of x is 0.05 to 0.50 from the conductivity
It is preferable that The current collector may be any material that is resistant to reduction, heat resistant, oxidation resistant, and conductive, but LaC
rO3, Co-based alloy containing Cr, Ni containing Cr
Base alloys, metal Cr, etc. are preferably used.

Metals that reduce the contact resistance of the cathode by being present at the electrolyte/cathode interface and the cathode/current collector interface include Pd, Cr, Mn, and Ti.
, Zn, Nb, and Ta. In addition, the present inventors have also discovered Pt, Co, In
, Sn was separately disclosed (Patent application No. 2-1)
No. 10482 and No. 2-110483), it was also found that metals such as the above-mentioned Pd are also effective.

[0008] Pd, Cr, Mn, Ti, Zn
, Nb 2 and Ta to the electrolyte surface, cathode surface, or current collector surface may be sputtering, electron beam evaporation, or the like. Note that the surface of the current collector to which Pd or the like is applied is also effective even on a surface that does not come into contact with the cathode. This is because at high temperatures during use of a high-temperature fuel cell, a portion of Pd and the like diffuses and moves to the interface between the current collector and the cathode.

[0009] Pd, Cr, Mn, Ti, Zn
, Nb and Ta, the application amount of at least one of them is:
It is not necessary to form a layer at the interface between the cathode and the current collector or electrolyte, and the presence of a layer has the effect of reducing contact resistance. The upper limit is La1-x SrxMO3 as cathode
It is sufficient as long as it does not impede the characteristics of.

0010

[Action] Pd, Cr, Mn, Ti, Zn, N
The presence of at least one of b and Ta at the electrolyte/cathode interface and cathode/current collector interface reduces the contact resistance of the cathode at these interfaces, improving the output of the fuel cell.

[0011]

EXAMPLES Example 1 A solid oxide fuel cell was manufactured according to the assembly pattern shown in FIG. As the solid electrolyte plate 11, a plate-like material of partially stabilized zirconia, which is zirconia added with 3 mole percent of yttria, and having dimensions of 50 x 50 x 0.2 mm was used. La0.9Sr0.1MnO3 powder (average particle size approximately 5μ) on the oxygen passage side
m) is dispersed in an organic binder to a thickness of 0.1 to 0.5
Ni is applied to the hydrogen passage side to form cathode 12.
A cermet mixed powder of /ZrO2 (9/1 weight ratio) was dispersed in an organic binder and applied to a thickness of 0.1 to 0.5 mm to obtain an anode 13. The current collector 14 is a flat plate made of a Ni-based heat-resistant alloy with dimensions of 50 x 50 x 5 mm with a groove of 2.0 mm deep as a gas flow path, or it is made by applying Pd paste on the contact surface with the cathode. Using.

This solid electrolyte plate 11 and current collector 14 are shown in FIG.
A glass paste having a softening point of about 800° C. was applied between the solid electrolyte plate 11 and the current collector 14 for gas sealing. This glass paste softens at the operating temperature of the battery, 1000° C., and seals in gas. A cylindrical alumina manifold 22 shown in FIG. 2 was attached to the battery thus assembled. The contact portion between the manifold 22 and the battery body 21 was coated with ceramic paste, dried, and bonded, and then glass paste was further coated to seal the contact portion with gas. A platinum lead wire was welded to the electricity outlet for electrical connection. In the figure, 23 is a hydrogen inlet, 24 is an unreacted hydrogen outlet, 25 is an oxygen inlet, and 26 is an unreacted oxygen outlet.

The fuel cell thus produced was heated. The glass paste was heated at a rate of 1°C/min from room temperature to 150°C to evaporate the solvent of the glass paste. 150~3
The temperature was raised at a rate of 5°C/min up to 50°C. At temperatures above 350°C, there is a
The temperature was raised to 1000°C at a rate of 5°C/min by flowing nitrogen gas. Thereafter, it was stored at 1000°C, hydrogen was flowed to the anode side, and oxygen was flowed to the cathode side, and power generation was started. The open circuit voltage was 1.25 V in all cases, and the gas cross leak was 0.5% or less of hydrogen.

[0014] La0.9Sr0.1Mn on the cathode 12
Using O3 powder (average particle size approximately 5 μm), N was applied to the current collector 14.
The discharge characteristics when the i-based alloy is used as is is shown below. The ohmic resistance of this battery was 70 mΩ according to the current interrupter method.

Further, when Pd paste was applied to the contact surface of the current collector 14 with the cathode 12, the discharge characteristics were as follows, and were improved compared to when the current collector 14 was used as is. The ohmic resistance of this battery was as low as 45 mΩ according to the current interrupter method.

Example 2 A solid oxide fuel cell was manufactured in the same manner as in Example 1, except that Ti was used instead of Pd, and it was attached to a manifold. The produced fuel cell was heated in the same manner as in Example 1. That is, the glass paste was heated at a rate of 1°C/min from room temperature to 150°C to evaporate the solvent of the glass paste. 150
The temperature was raised at a rate of 5°C/min from °C to 300°C. 3
At temperatures above 00°C, nitrogen gas is flowed into the hydrogen passage to prevent oxidation of the anode, and the temperature is increased to 1000°C at a rate of 5°C/min.
The temperature rose to Thereafter, the temperature was maintained at 1000°C, hydrogen was flowed to the anode side, and oxygen was flowed to the cathode side, and power generation was started. The open circuit voltage is 1.25V, and the gas cross leak is 0.2V for hydrogen.
It was less than 3%.

The discharge characteristics when Ti is sputtered onto the separator are shown below. Similarly, the ohmic resistance was 50 mΩ.

[0018]

[Effects of the Invention] According to the present invention, the contact resistance between the cathode and the current collector or electrolyte of a high-temperature fuel cell is reduced;
Battery output is improved.

[Brief explanation of the drawing]

FIG. 1 is a developed configuration diagram of a flat plate fuel cell.

FIG. 2 is a perspective view showing a state in which a manifold is attached to a flat plate fuel cell.

[Explanation of symbols]

11...Electrolyte 12...Cathode 13...Anode 14, 15, 16... Current collector 14a, 14b, 15b, 16a... groove

Claims (1)

[Claims] Claim 1: A high-temperature fuel cell having a structure in which a cathode is formed on one surface of a high-temperature electrolyte and a current collector is brought into contact with the cathode.
rxMO3 (wherein M represents Mn, Co or Ni) and faces the cathode of the electrolyte,
Pd, Cr, Mn, Ti,
A high temperature fuel cell characterized in that at least one of Zn, Nb and Ta is present.